The present application relates to sources of heat energy and, more particularly, to a novel monolithic integrated heat source.
It is well known that a wide variety of appliances require the conversion of electrical energy into heat energy. Among these appliances are: clothes irons, food-warming trays, toasters, electric frying pans, crepe makers, waffle irons, toasted sandwich makers, mullion heaters in no-frost refrigerators, frost eliminators in air conditioners, clothes dryers, vaporizers, dishwasher and oven heating elements, crock pot heaters, hot shaving lather makers, local room heaters, roof-eave and sidewalk de-icers, and many other appliances, of which the foregoing is by no means an exhaustive list. Many problems are, however, encountered with the use of conventional apparatus for conversion of electrical energy to heat energy.
As an example, the conventional appliance oven is a structure generally consisting of an insulated metal box having at least one heating element within the central cavity thereof. Thus, space must be provided, within the oven cavity, in which to position the heating element, thereby effectively reducing the total available space in which food to be cooked can be placed within the oven cavity. In the small toaster-type ovens, the heating elements, which may be CALROD.RTM.s and the like heating elements, may occupy as much as 25% of the usable volume in the oven cavity. Further, since the heating element is a lineal source, uneven heating of the cavity, and of the food being cooked therein, occurs; this phenomena is commonly called "hot spots." Additionally, the heating element can be contacted by user personnel; as the heating element ordinarily is powered by eventual connection to commercial power means, potentially lethal voltages may be contacted by the user personnel, whereby the danger of electrical shock is always present.
In home ovens of the self-cleaning type, additional problems occur, due to the inability to raise the temperature of the oven walls evenly. Certain oven wall areas, such as near the oven front door, will be colder than the remaining wall areas, whereby additional heating elements, such as mullion-type heaters, will be required. This adds additional cost of materials and labor, as well as necessitating additional power consumption. If the material to be self-cleaned from the oven falls into the class of "sugars," initial application of heat during the self-cleaning process causes an ash to form on, or over, the surface of the material to be cleaned and effectively insulates the bulk of that substance from the convection-transported, externally-applied heat energy utilized in the self-cleaning process. Therefore, additional time and energy is required to clean materials of this class from the oven walls. Because of the relatively high-cleaning temperatures required, on the order of 800.degree. F., the oven must be equipped with oven door glass heat shields, safety door latches and redundant temperature controls, in addition to a greater amount of heat insulation than would normally be required by a conventional oven, in order to keep the temperature of the air surrounding the oven from becoming dangerously high and presenting a fire and/or personnel hazard.
Heat-energy sources, for use in ovens and the like appliances, having a reduced degree of safety hazard, as well as being less costly and energy consumptive, are therefore highly desirable.